<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        
    </style>
</head>
<body>
    
</body>
<script>
    var str1 = "hello";
    var str2 = new String("world");     // 字符对象

    console.log(str1)
    console.log(typeof str1)
    console.log(str1 + 1)

    console.log(str2)
    console.log(typeof str2)
    console.log(str2 + 2)
</script>
</html>